Epithelial responses of rabbit tongues and their involvement in taste transduction

The response of rabbit tongue, placed in a modified Ussing chamber, to salts [KCl, NaCl, NH4Cl, tetraethylammonium chloride (TEACl)], sweeteners (D-glucose, sucrose), acid (HCl), and a bitter tastant, quinine, was investigated for the first time. These experiments were conducted to further explore the new paradigm of taste transduction that correlates changes in the electrical behavior of lingual epithelia with neural responses. In addition, the responses of rabbit tongue data were compared with previously published data on dog and frog tongues. When increases in short-circuit current (Isc) for rabbit tongue induced by hyperosmotic concentrations of several salts were compared, the following sequence was found: KCl greater than NH4Cl greater than NaCl greater than TEACl. These results are consistent with previously published integrated chorda tympani responses (ICTR) as well as behavioral studies that showed that rabbits prefer KCl to NaCl with their natural diet. Pharmacological studies using ouabain and amiloride suggest that K and Na are traversing rabbit tongue through different pathways. The maximal stimulation of Isc by D-glucose and sucrose (in 50 mM NaCl) was significantly smaller than those measured for KCl and NaCl. The rabbit tongue was sensitive to HCl at concentrations less than 1 mM in agreement with ICTR measurements.